Fish Anatomy: External and Internal

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Fish Anatomy External and Internal
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Outline

• General review of fishes
• External anatomy
• How to key out fish using external
  characteristics
• Internal anatomy
• What well look for during dissections
• What youll write for your fish paper

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Jawless Fish

• Lampreys and hagfishes
• Primitive
• No jaws suctorial mouth
• No paired fins
• No scales
• Hagfish
• Blind
• Scavengers
• Lampreys
• Parasitic attach to hosts and suck body fluids

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Jawless Fish Anatomy
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Cartilaginous Fish

• Skeleton made of cartilage
• Well-developed lower jaw
• Males have claspers for internal fertilization
• Placoid scales (skin feels like sandpaper)
• Paired and unpaired fins
• Includes sharks, skates, rays, and chimaeras

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Shark Anatomy
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Bony Fish

• Skeleton made at least partially of bone
• Dorsal, anal, and caudal fins
• Paired pectoral and pelvic fins
• Bony gill cover (operculum)
• Lateral line (vibration detection)
• Cycloid (smooth) or ctenoid (spiny) scales
• Swim bladders
• Variety of shapes

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Bony Fish Anatomy
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Comparison of Scales
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How to Key Out (Identify) Fish

• Sequenced observations of key characters like a
  Choose Your Own Adventure book
• Dichotomous taxonomic key at each step of the
  Choose Your Own Adventure, you never have more
  than two choices
• Start with general characteristics, and progress
  to finer characteristics

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Examples of Characters

• Anal soft rays
• Gill rakers on first gill arch
• Scales along lateral line
• Pelvic fins present or absent, thoracic (chest
  area) or abdominal (belly area)
• Percent of head or eye diameter of standard
  length
• How many dorsal fins? What are they made out of?

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Example of Character List
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Fish Internal Anatomy

• Two-chambered heart and gills circulation, gas
  exchange
• Stomach / intestine / liver digestion, breakdown
  of macromolecules into molecules the fish can use
  for growth, energy, etc.
• Swim bladder buoyancy
• Red muscle slow twitch, holds lots of oxygen,
  endurance swimming
• White muscle fast twitch, holds little oxygen,
  fast bursts of swimming

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Things to Look For During Dissections

• Operculum
• Type of scales
• Lateral Line
• Countershading
• Internal organs
• Swim bladder
• Red and white muscle
• Body and tail shape (how do these affect
  swimming?)
• Mouth shape (how does this affect feeding?)
• Gill area in relation to activity level of fish

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Fish Writing Assignment

• Page 48 in your reader
• Pick two fish. Write 2 pages about the feeding
  strategy of one, and the locomotion strategy of
  the other
• Can use the Internet, cite all sources
• Be careful not to plagiarize easy to do with
  this assignment!
• Include a picture of each of your fish
• Be as detailed as possible, but make sure you
  understand what youre writing

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Fish Body Forms
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Fish Mouth Parts
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Fish Tails